It is known that the sporogenous bacillus Bacillus thuringiensis (Bt) produces, during the sporogenesis step, parasporal crystals of proteinic nature and displaying an insecticide activity against a large number of insects belonging to the orders of Lepidoptera, Diptera and Coleoptera. Such crystals, when ingested by an insect sensitive to their activity, cause irreversible damages to its intestinal mucosa, with the insect consequently stopping feeding and undergoing death.
Many varieties of Bt are known, which differ from one another on the basis of biochemical and/or physiological parameters, and of their specific/selective insecticide activity. Some of these varieties are traded as formulates for use in the fight against insects.
The Bt varieties known heretofore are subdivided on the basis of their specific/selective activity, into three pathotypes:
______________________________________ Specific insecticide Pathotype activity Main varieties ______________________________________ A Lepidoptera kurstaki B Diptera israelensis C Coleoptera tenebrionis san diego ______________________________________
As pathotype C, endowed with specific activity against coleopters, only two varieties are known in the art, i.e., var. 1 tenebrionis, claimed in European patent application No. EPO 149,162 and var. san dieco, claimed in EPO 202,739.